Curtain fastener



FIG. 1 is a front perspective view of a curtain fastener showing my new design;

FIG. 2 is a top view thereof;

FIG. 3 is a front view thereof;

FIG. 4 is a right-side view thereof;

FIG. 5 is a left-side view thereof;

FIG. 6 is a rear view thereof; and,

FIG. 7 is a bottom view thereof.

The broken lines are for illustrative purposes only and form no part of the claimed design. 

I claim the ornamental design for a curtain fastener, as shown and described. 